1. Field of the Invention
The present invention relates to a digital signal processing apparatus adapted for use in a digital video tape recorder or the like.
2. Description of the Prior Art
In an 8-mm video tape recorder (VTR), it is generally customary that a servo pilot signal generated for automatic tracking in a recording/playback mode is combined with a recording information signal on a time basis to produce a composite signal, which is then recorded on a magnetic recording medium such as a magnetic tape.
A conventional signal processing apparatus for performing such a recording operation is shown in FIG. 5, and examples of signal waveforms processed in this apparatus are shown in FIG. 6.
The signal processing apparatus of FIG. 5 includes an analog multiplexer 2 and a recording amplifier 4, in which an analog recording signal Sa and an analog servo pilot signal Sb as, for example, shown in FIGS. 6A and 6B, respectively, are controlled so as to have respective predetermined levels by amplifiers (not shown) and are then supplied to the analog multiplexer 2. Thereafter, the analog recording signal Sa and the analog servo pilot signal Sb are combined with each other on a predetermined time basis through the use of an analog switching signal Sc, such as the switching signal shown in FIG. 6C to produce a composite signal Sd. The composite signal Sd is current-amplified by the recording amplifier 4 and supplied via a rotary transformer (RT) 6 to a magnetic head 8, whereby the signal Sd is recorded on a magnetic tape Tp.
The analog pilot signal Sb has a level higher than that of the recording signal Sa as recorded on the magnetic tape Tp and, as a result, an increased carrier-to-noise ratio is attained when the analog pilot signal Sb is read out later.
In the conventional signal processing apparatus described above, the analog recording signal Sa supplied to the analog multiplexer 2 may lie in a frequency band of, for example, 20 to 30 MHz, while the analog servo pilot signal Sb may lie in a frequency band of several MHz. For amplifying such wide-band signals to desired flat levels, a high-frequency amplifier having a relatively complicated circuit configuration is needed. As a result, it is very difficult if not impossible to meet the recent requirements regarding dimensional or scale reduction of both the apparatus as a whole and the signal processing unit. Furthermore, another disadvantage exists in that characteristic variations are prone to occur due to temperature fluctuations and so forth which prevent high reliability from being attained.